306 Causes and Course of Organic Evolution 



As will be again emphasized later on, vre would view the 

 above four large and preponderatingly marine groups as of 

 primitively fresh-water origin, and as still including fresh- 

 water connecting links with the yellow, the brown, the brown- 

 green, the pink, the red-green, and the green Cyanophycece. But, 

 while we have abundant evidence to show that the above 

 four groups, on passing from a fresh-water to a marine exis- 

 tence, branched out into many genera and species that con- 

 tributed to the large existing total of 4233 species, few observers 

 have ever regarded them as the originators and ancestors 

 of the dominant lines of ascent that later gave rise to the bry- 

 ophytic or moss series, the pteridophytic or fern series, and 

 others still higher. These have generally been sought for, and 

 we believe rightly, amongst some ancient representatives of the 

 Chcetophoracece and Coleochcetacece, both fresh-water genera. 



Now we hope to show that the great processional change 

 from fresh to salt water that the above four groups exhibit 

 has been gone through again and again in the history of animal 

 groups, which starting from more primitive fresh-water types 

 have passed on to a salt-water existence, and have then evolved 

 a wealth of marine genera and species, but have failed to evolve 

 higher groups than themselves. 



Morphologically and taxonomically then we would regard 

 the fresh-water Cyanophycese as the ancestors of higher algoid 

 organisms, while the conclusions of most workers in the past, 

 that the green fresh-water algae have given rise to higher pal- 

 ustral and later to land forms, seem fully warranted by evidence 

 from every side. The morphological evidence in favor of 

 continuity from the Cyanophycese to the highest algae can 

 now be studied. 



Each simple spherical cyanophyceous organism like Chroo- 

 coccus or Gloeocapsa shows mthin the mucilaginous wall a 

 cylindrical zone, as Hegler has pointed out, of yellowish, yel- 

 low-broT\Ti, yellow-green, blue-green, or pink-green color — the 

 chromatophore. This consists of a nearly homogeneous plas- 

 matic ground-substance in wliich chlorophyll and phycocyanin 

 bodies are closely distributed. The chlorophyll pigment evi- 

 dently enables the plasmatic substance to elaborate glycogen, 



